Special Circumstances (WK 4) Flashcards
Which structure does the coronary venous blood use, and to drain into where?
Uses the coronary sinus to drain into the right atrium.
What happens in coronary heart disease?
Area of cardiac muscle deprived of blood due to a blockage in a coronary artery.
What are some common areas of blockage in CHD?
- Left coronary artery
- left anterior descending artery.
What are the special adaptations of coronary circulation?
- High capillary density
- High basal blood flow
- High O2 extraction rate
Because of this, the only way to supply extra O2 to the myocardium is by increasing the blood flow and thus o2 content to it.
What intrinsic mechanisms control coronary blood flow?
- Reduced P02= vasodilation of c arteries.
- Metabolic hyperaemia- matches flow to demand
- Adenosine- vasodilator.
What extrinsic mechanisms control coronary blood flow?
Sympathetic vasoconstrictor tone Overidden by metabolic hyperaemic drive.
So sympathetic stimulation causes- coronary Vasodilation
Adrenaline- B2 adrenoceptors that can cause vasodilation
When does peak coronary artery blood flow occur?
in Diastole. A very fast HR (arrhythmia) means reduced coronary blood flow.
Which type of arteries is the brain supplied by?
- internal Carotid arteries
- Vertebral arteries
What is the circle of Willis?
Basal arteries (formed from vertebral arteties) and carotid arteries anastomose to form the circle of willis. Major coronary arteries emerge from the circle.
What are the two types of stroke? Explain each type.
Hemorrhagic- blood leaks out of damaged artery wall.
Ischaemic- Blood clot forms an atheroma on vessel wall. could also be an emboli stuck in the cerebral arteries.
What happens in auto-regulation of cerebral blood flow in response to MAP?
MAP too high- Vasoconstriction
MAP too low- Vasodilation
Autoregulation maintains cerebral flow in any MABP changes between 60 and 160mmHg.
What happens in the brain if MAPBP is below 50mmHg?
Confusion, fainting.
Brain damage if not quickly sorted
What other factors regulate cerebral blood flow?
Higher PCo2–> Causes cerebral vasodilation
What is regional hyperaemia?
Blood flow increases to areas of the brain that are more active.
What is the effect of intracranial pressure on cerebral blood flow?
Decreases cerebral blood flow.
What are some features of the blood brain barrier that helps it to maintain brain functionality?
V permeable to 02 and CO2
Impermeable to ions, proteins etc (protects brain from fluctuating ion levels in blood)
Glucose crosses barrier via diffusion through carrier molecules.
What systemic adaptations protects the lungs from pulmonary oedema?
Systemic absorption exceeds filtration rate.
What is the effect of hypoxia on pulmonary arterioles?
Vasoconstriction. Diverts blood away from poorly ventilated areas of the lung.
What happens to skeletal muscle blood flow in exercise?
- Metabolic hyperaemia overides vasoconstrictor tone- Vasodilation.
- Circulating Adrenaline stimulates B2 adrenoceptors- vasodilation
- Increased cardiac flow= increased blood flow to skeletal muscle.
Overall effect- increased blood flow to skeletal muscle.
What does the skeletal muscle pump do?
Contraction of large limb muscles increases Venous Return to the heart.
Helps in: Postural hypotension. fainting.
What are varicose veins?
Pooling of blood in lower limbs if valves become incompetent.
Doesn’t usually lead to lower CO–> Cos of compensatory increase in blood volume
